Licencies do not usually require written tenancy agreements. This does not mean they shouldn’t. Bed and breakfast accommodation, for instance, would most likely not require a written tenancy agreement. The same goes for rooms let to lodgers. It is advisable, however, to get a lodger’s agreement to be on the safe side.
That being said, it is always best have a written, signed tenancy agreement to protect all parties involved should a dispute arise in the future. Sure, nobody wants to encounter a problematic landlord, tenant, or even a problematic experience. Being prepared for such eventualities is the smartest thing to do.